44 Proceedings of Indiana Academy of Science 
of abundantly parasitized birds, such as cormorants, gulls or pelicans, 
have been frightened. 
Normal migration from bird to bird occurs when in contact, among 
gregarious groups, or at mating from female to male, or vice versa, or 
to the fledgling birds at the time of brooding. 
Upon the death of the host some of the lice wander off the cold body 
with little chance ever to become relocated within the three or four days 
in which they can live under the most favorable conditions. Many 
usually remain, but only to perish within ten days, firmly gripping 
feather barbules between their jaws. Those which could have subsisted 
upon the foods of their ancestors in a free range have long since passed 
away, and only these remain whose food and living conditions have 
been unchanged for so long a time that individuals having variable 
tastes have been bred out. 
The Mallophaga are capable of living on certain hosts toward 
which they have developed a certain physiological fitness. The curious 
sensitiveness to differences in composition of host hair and feathers or 
skin and oil, etc., is so marked that those of our number who, in the 
course of a hunting trip, or in their collection, inadvertently became the 
temporary hosts of bird- and mammal-infesting mallophaga and ano- 
plura found these parasites as eager to escape as we were to have them 
do so—or in the failure of which they died in a few hours. The real 
reasons for failure to live are not apparent and we conclude that it 
represents a particular physiological fitting in addition to the presence 
of the number, size and shape of claws and conformation of clinging 
devices or spine-hairs set at a particular angle to afford security of 
position on the body. If the species common to wild birds are trans- 
ferred experimentally to guinea pigs, which ordinarily support two 
species of mallophaga, or to our common poultry, they are unable to 
maintain themselves even though the skin and hair, or the feathers, 
would seem to serve the same purpose, as food. It is likewise true that 
birds of prey do not fall heir to the parasites which were common +o 
the birds or mammals upon which they prey, though to this there are 
occasional exceptions. 
The progeny of permanent ectoparasites represent a closely inbred 
strain that is isolated biologically from the rest of the individuals com- 
prising the species which it represents and with it go all the possi- 
bilities that are associated with the fixation of hereditary qualities. In 
a sense the relationship represents an environment that is comparable 
to island life. On such island the individuals pass a life that is monot- 
onously alike whether the bird is aerial, terrestrial or aquatic. 
Kellog, who has described hundreds of new species of mallophaga, 
asserts that the relative isolation plays a conspicuous role in the forma- 
tion of species. He and other workers ascertained that closely related 
birds, whatever their geographical range, are the hosts of closely re- 
lated mallophaga. Thus, the species, Lipeurus baculus, which occurs 
on the domesticated pigeon, has been collected from nineteen of the 
forty pigeon host-species that range through Europe, Asia, Africa, 
North America, Malaysia, Australia, Madagascar, and the Galapagos 
Islands, and that of the twelve species which occur on the domesticated 
